In general, development of wireless local area network (WLAN) technology has advanced in three directions.
One direction indicates technology for improving a transmission rate and includes WLAN technology using a 60 gigahertz (GHz) band and WLAN technology using a 5 GHz band. Another direction indicates wideband WLAN technology using a frequency band under 1 GHz to extend coverage when compared to conventional WLAN technology, and still another direction indicates technology for reducing link set-up time of a WLAN system.
Wideband WLAN technology is required to accommodate a remarkably larger number of stations (STAs) than established WLAN technology.
Further, the wideband WLAN technology may need to support STAs with various types of services, such as, offloading terminals and sensor terminals, traffic types, and power saving demands.
Therefore, advancements are being made in a wideband WLAN system for reducing collisions in channel access and achieving efficient power saving by grouping a plurality of STAs. Also, advancements are being made in the wideband WLAN system for using restricted resources such as a bandwidth, a time, and a power.